Electrical transformer.



Patented M3112, 1915.

Fig. 2

E@ HAEFELY. ELECTRICAL TRANSFORMER. APPLICATION FILED 11111.10, 1912.

Fig. '1

EMIL HAEEELY, or BASEL, SWITZERLAND, iis/SIGNOR To wEsTrNGH'oUsE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA.

ELECTRICAL TRANSFORMER.

LSQZS.

Specification of Letters atent.

Patented Man 2, 1015,

Application led January 11.0,l 1912. Serial No. 670,531.

Toa/Z whom it may concern:

Be it known that I, EMIL HAEFELY, a citizen of the Republic of Switzerland, yand a resident of Basel, Switzerland, have invented a new and useful Improvement in Electrical Transformers, of which the following is a specification.

It has heretofore been usual in transformers to insulate the high tension and low tension windings from each other and from the iron core by means of sleeves composed of tough paper or cardboard, either alone or in combination with mica, or of mica only, these sleeves being disposed around the core and between the high and low tension windings. Such sleeves, and sleeves made of other tough insulating material, are however unsatisfactory in practice when exposed to high electromotive forces, such for instance as from over 20,000 to 25,000 volts, as they permit vstat/ic discharges from the other coils of oney of the branches of the high tension winding to creep'over orrbeneath their surfaces, with the result that, the insulating material becoming carbonized, a path is sooner or later provided for the high tension current, over which a. disruptive discharge or short circuit from the high'tension to the low tension winding or the core may eventually take place. rlhese remarks are equally applicable whether thesurface of the sleeve be rough or smooth and whether i i it be cooled by air or by oil.l In order as far c the most suitable. Moreover, the high poteni for testing purposes andin conductors for as possible to prevent the formation of such a creepage path it has been proposed to allow the sleeve to project to a certain eXtentbeyond the coils of the high tension winding or to arrange the parts ofthe sleeve at the 4side adjacent to the high tensionfvwinding in the form of steps, and thus as far as possible to prolong the path along which creeping may take place in accordance with the potential difference between the adjacent windings. This, however, necessitates a greater space between the winding and the core than is reallyrequisite ifonly direct short-circuiting, not due to the existence of creeping surfaces, is taken into account, thus leading to a construction of transformer which, while'more expensive, is by nolmeans tials frequently employed in transformers long distance transmission involve the use of thick-Walled insulating Sleeves, which however are subject to various defects.

Although it is quite practicable, by means of suitable appliances, to manufacture stout but still absolutely homogeneous sleeves, it

should not be forgotten that this can. be

of the sleeve, but first through several layers of insulating material, and then through I the interior of the sleeve in the direction of the core. Thick-walled sleeves are moreover subject to the great defect of generating on their own account a fairly large amount of heat, due to dielectric hysteresis, which heat in the case of oil-transformers acts to increase the temperature of the oil.

Now this-invention relates to an insulating sleeve which is especially suitable for oil-transformers of the core-type exposed to high electro-motive forces and by means of which both the risks due to the formation of a creeping surface or ath and those due to the generation of heat Ey dielectric hysteresis are considerably diminished, if not entirely obviated. The sleeve is made throughout of insulating material, but it is not entirely homogeneous in the direction of its thickness, but is partially of hard and partially of soft texture. The hard layer imparts to the sleeve the necessary mechanical rigidity, while the soft layer, which consists of an absorbent or suction-producing material adapted to become completely saturated with oil, and yet to retain its softness, serves to eect the main insulating work of the sleeve, that it to say, it is subjected' to ythe highest potentials at which brush or other static discharges mightl take place in the transformer.

The accompanying drawing illustrates several sleeves constructed in accordance with this invention, Figure l being a verti-Y cal section of a sleeve in its simplest form. Fig. 2 shows in vertical section a sleeve having Mseveral different layers.

soft layer b of an absorbent substance, such,

Figs. Y3 and 4 show respectivelyin verticaland horizontal sections a sleeve placed between the windings of an oil-transformer of thecore-type, andM Figs. 5 and 6 arevertical sectional vviews of further modified `forms of insulating barrier. In all cases the form of cross section of thasleeves may be dierentfrom the circular form.

In all these examples, the inner layer a of the sleeve is hard and may consists of tough either alone or in combination with Papel" It is surroundedby a comparatively mica.

for instance, as textile fabric, blotting paper, cellulose board or the like.

For covering the soft layer b and for protecting it against deformation and against the pressure of the high tension winding, it is surrounded, as shown in Figs. 2, 3 and 4, by a comparatively thin, but hard and rigid layer c which may consist either of the same material as the layer a or of a band of the transformer in order to prevent the formation of a creeping surface. The high tension winding is represented in-this gure, aswell as in Fig. 4, bythe-letter k, while the low tension winding has the letter a and l the core the letter The surface-of the uncovered part of the layer b which projects beyond thev winding 'h and -which is 'saturated with oil, is in direct contact with the oil which surrounds .the sleeve when in use in the transformer, with the result that the '1 circulation of the oil yis promotedand consequently the heat is led awayfrom the hard 'layer a in a most advantageous manner.

With any of the above described insulating barriera-it is'substanti'al-l'y, if not entirely, impossible for `heat tol''be generated in the barrier -itselflby dielectric hysteresis ondly because the heat 'can'vbe conducted I: away yfrom the hard layer a'of'thev sleeve-f'- vmore rapidly and eectually than wouldbe or otherwise, first on account. of the soft and sponge-like character of the layer bwhich is saturated Acontinuously' `with oil, and secthe case if only its' exterior and interior 'sur-L faces were in contact. with .the oil in' the transformer.- p By means of sleeves oftlrce described `there can' vbe obtailedgreater security lagainst the riskof c eeping from the high tension to ^the low tension winding'or to the iron core than is obtainable by means of sleeves of;the usual kind, while, should the same degree of security-as can be obtained bymeans of ordinary sleeves, be considered suiiicient, the dimensions and cost of the whole transformer may be considerably reduced. A

The objects of the invention fulilled by a sleeve having the soft layer within the 'hard one as shown in Fig. 5; or a soft layer may be arranged on both sides of the hard layer Aas' shown in Fig. 6.

Having now particularly described and ascertained the nature of my said invention may also be and in what manner the same is to be performed, I declare that what I claim is 1. An insulating structure 'for electrical apparatus comprising a layer of hard rigid non-porous insulating material, a layer of soft porous insulating material thereby, and an' oil bath.

supported 2. An insulating structure for electrical l apparatus comprisingl a layer of rigidnom' porous insulating material, a layer vof absorbent insulating material supportedthere= by, and a bath of insulating iuid.`

3. An insulating structure for electrical f apparatus comprising alayer of insulating material that imparts 'rigidity vto the bar-v rier, a layer of absorbent insulating mafterial, and van immersionbath of insulatingY fluid. t

4. An insulating structure for electrical apparatus comprising a sleeve of insulating material that imparts rigidity to the barrier, a sleeve of 'absorbent insulating maieril, and-an immersion bath of insulating v A5'. An -insulating'structure `for electrical apparatus comprising an'oil bath, a sleeve` of insulating material thatlimparts'rigi'dity to the barrier, and a sleeve of material that i Pabsorbfsoil and thereby constitutes the prin` cipal' insulating medium.

6. An insulating structure for' electrical apparatus4 comprising an oil bath, two 1 lspaced layers ofrigid nonp'orous insulating material, and a''layer of absorbent insulating material between the aforesaid layers'.

.7. ilninsulating structure for -eletrical apparatus comprising an oil ba'tli, two

' spaced layers of rigidinsulating material,

andl a layer ofA absorbent insulating mafterialbetween thev aforesaid' layers one of therigid layers beingv shorter than the others.

8., In an electrical thev combination with parts to be insulated from one another,

of'aninterposed insulating .structure comprising a layer vof rigid Yinsulating material,

a layer of absorbent insulating material, and

an oil bath.

9. Ina'n electrical device, the combinatibn i with parts to be insulated fromvone another,

10 sulating material, a layer of absorbent insulating material between the aforesaid layers, one of the rigid layers being shorter than the btvhers, and an oil bath.

In testimony whereof I have signed my name to this specification in the presence of 1 5 two subscribing witnesses.

- EMIL HAEFELY.

Witnessesz HANS FICKELBERGER, GEORGE GIFFORD. 

